People walk in the Place de la Bastille in Paris on December 16, 2012 during a demonstration …

Passions and tensions are rising in France ahead of an expected giant weekend rally against the government's plan to legalise same-sex marriage and adoption that has angered influential Catholic and Muslim groups.

France's parliament is to debate the government's "marriage for all" bill early this year -- one of the key electoral pledges of Socialist President Francois Hollande -- which has run into fierce opposition in this predominantly Catholic country where Islam is the second biggest faith.

Preparations for Sunday's rally are gaining steam with protesters nationwide hiring coaches and high-speed trains to gather in the French capital to voice their opposition.

They are also distributing hundreds of thousands of leaflets.

"It's a real wake-up call," said Gonzague de Chanterac, whose blog to rally support for the protest has received 6,000 hits in the month running up to the march.

"We have all rallied around the fact that it is touching a very important link which could destabilise the family," said Rachid Laamarti, who has been among those organising protests on behalf of the Muslim community in the northern city of Lille.

The controversy over the highly divisive issue gained momentum over the weekend after the education minister asked Catholic schools to drop a plan to discuss the bill in schools, evoking France's traditional line of separation of the Church and the state.

Eric Labarre, the secretary general of the national Catholic school system, stirred up a hornet's nest in December by asking teachers to discuss the issue.

He said in a letter that schools should take "appropriate steps to ensure everyone has the right to make an informed decision over the choices the government is considering today".

But Education Minister Vincent Peillon sent a speedy response saying that would not be appropriate, recalling that Catholic schools were "under contract with the state" and "must respect the principle that everyone has the right to neutral and free thought".

France's Catholic schools are all private but receive some state funding and have to follow the national curriculum although they are allowed to impart religious instruction.

"But we also have to (respect) the fact that we all live in the same place and that the stateHollande also took the same line saying "Secularism is a Republican value..

"We have to make sure that all ways of thinking are respected and that all religions can be respected," he said as well as both private and public educational institutions adhere to a principle called neutrality."

Labarre however struck a defiant note Tuesday, saying he had not committed any breach by sending out the letter, adding: "I would not change a comma. I don't regret anything."

French Muslim groups are joining in the opposition. The call has been led by the influential Union of French Islamic Organisations (UOIF) which urged co-religionists to join the march.

"This bill, if it passes, will disrupt family and social structures and civil law dangerously and irreparably."

The head of the French Roman Catholic Church, Cardinal Andre Vingt-Trois who has been vocal in his opposition of gay marriage, as well as chief rabbi Gilles Bernheim and Muslim Council head Mohammed Moussaoui will not take part in the street protests.

Far-right leader Marine Le Pen will also not be attending but her National Front party has authorised those wanting to take part to do so despite officially taking the line that it was not backing the march.